Analysis of hydroxy-cocaine metabolites as evidence of cocaine consumption: identification by parent ion search and quantitation by liquid chromatography–tandem mass spectrometry in hair sample

Over the last decade, hair analysis has become a routine procedure in most forensic laboratories and, complementary to blood and urine, hair is a unique biological matrix which gives the opportunity to establish a temporal consumption profile. Despite hair is widely used to identify drug use, environmental contamination still continues to represent a challenging factor of this procedure, especially for cocaine. In order to distinguish between actual use and external contamination, several strategies have been proposed in the last few years, such as the evaluation of concentration ratio between cocaine (COC) and benzoylecgonine (BEG), the detection of norcocaine (NCOC) or cocaethylene (CE) or an extensive washing step to decontaminate hair prior the analysis. The aim of this study is the development of a quali-quantitative LC-MS/MS method able to detect hydroxy-cocaine metabolites, as specific markers of COC abuse, in hair samples from cocaine consumers, thus enabling unambiguous evidence of COC consumption. COC\u2010positive hair samples were tested using parent ion scan-based analysis to extract hydroxy cocaine metabolites target ions. Once identified, an LC-MS/MS method to quantify p\u2010 and m\u2010isomers of hydroxy COC, as well as hydroxy BEG and hydroxy NCOC was developed and validated. Analysis was performed on a triple quadrupole ABSciex Qtrap 5500 mass spectrometer operating in electron spray ionization (ESI) mode. The method was successfully applied to a large number of COC-positive hair samples, with the following preliminary results: - p-OH BEG: 0.23 \u2013 80.36 pg/mg; m-OH BEG: 0.23 \u2013 49.64 pg/mg - p-OH NCOC: 0.11 \u2013 43.34 pg/mg; m-OH NCOC: 0.28 \u2013 82.07 pg/mg - p-OH COC: 1.28 \u2013 1754.37 pg/mg; m-OH COC 0.63 \u2013 1038.29 pg/mg It was then introduced into a routine procedure for testing drug ingestion in order to evaluate for the first-time hydroxy metabolites ranges in hair and to avoid the risk of false positive in discussed COC\u2010positive cases